Abstract

This article presents the first projection, to our knowledge, of the intensity of religiosity in a population, which has a strong bearing on the critical question of the religious future of Europe. Spain has, in recent decades, simultaneously experienced rapid religious decline and marked demographic change through high immigration and declining fertility. To investigate future trends, we carry out population projections by religion and religiosity to the year 2050. We find that both fertility and immigration increase the share of the highly religious, as the more religious tend to have more children and immigrants tend to be more religious than non-immigrants. The non-religious population grows because people switch from religion to no-religion and because they are younger. Our findings suggest that in the longer term (2050), there may be growth in the no-religion population, a decline in the share of highly religious Christians, and moderate development of low religious Christians. The Muslim population would substantially increase, unless there is an end to migration and fertility differentials.